Bare glass fibers are substantially smooth rod-like members having surfaces which are highly hydrophilic in nature and thus will not typically exhibit a bonding relationship with polymeric materials sufficient to provide reinforcement properties thereto. That is, the lack of bonding between the bare glass fibers and the polymeric material causes the glass fibers and the polymeric material to separate from one another and thus are not useful for the manufacture of glass-reinforced product. It is conventional, therefore, to apply a thin layer of an aqueous size composition to the surfaces of the bare glass fibers, which composition is compatible with and serves to improve the bonding relationship between the glass fibers and the polymeric material. A thin layer of size composition serves an additional beneficial function. That is, during processing of the glass fibers into a form suitable for use as reinforcement for polymeric products, the fibers are exposed to abrasive contact with structural components utilized during processing. The size composition layer, therefore, also serves to protect the underlying bare glass fiber from abrasion damage which could otherwise occur during processing.
Sizing compositions typically employed as coatings for glass fibers have conventionally been aqueous-based formulations. The glass fibers are typically sized as formed, collected into a strand, and the strand is then wound around a take-up bobbin to form a substantially cylindrical package (conventionally termed a "yarn package"). The yarn package is then air dried or subjected to elevated temperatures so as to dry the aqueous size composition applied to the surfaces of the glass fibers forming the strand. In this regard, attention is directed to U.S. Pat. No. 3,816,235 which is expressly incorporated hereinto by reference.
As the reader can appreciate, considerable time and expense would be saved if a size could be employed which requires no drying and which could be directly blended into the polymeric material and molded therewith to provide satisfactory reinforcement. Our copending application Ser. Nos. 613,846 and 613,940 each filed on Mar. 24, 1984 relate to such desirable glass size compositions in that there is disclosed therein a non-aqueous, 100% solids formulation of a hot melt size for use in coating glass fibers so that the coated glass fibers can be satisfactorily employed as reinforcing media in an polymeric resin matrix.
The present invention is directed to a similar genre of hot melt coatings for glass fibers described in Ser. Nos. 613,846 and 613,940 in that it relates to a non-aqueous 100% solid hot melt formulation for coating glass fibers. The specific improvement of this invention, however, relates to a hot melt formulation suitable for direct blending with a white thermoplastic resin such that the coated fibers will not detract from the visible whiteness of the resulting glass fiber-reinforced product.
Accordingly, there is provided by the present invention a non-aqueous coating for glass fibers consisting of a 100% solids formulation of an organosilane, a maleic anhydride-modified polyolefin, a hydrogenated hydrocyclic hydrocarbon thermoplastic resin, an ethylene-ethylacrylate copolymer, a microcrystalline wax, a viscosity-reducing agent, an antioxidizing agent, and a whitening agent. The coating of this invention can thus be applied as a size for glass fibers and the resulting sized glass fibers can be incorporated into a compatible polymeric resin matrix to provide a glass-fiber reinforced product.
These and other aspects and advantages of the present invention will become more clear to the reader after consideration is given to the detailed description of the preferred exemplary embodiments thereof which follow.